1. Field of the Invention
The present invention relates to an insertion device for a deformable intraocular lens that is inserted into the eye in place of the natural lens when the latter is physically extracted because of cataract, for a deformable sight corrective lens that is inserted into the eye only for the purpose of sight correction, or for a like deformable intraocular lens.
2. Description of the Related Art
In 1949, Ridley became the first to implant an artificial lens; i.e., an intraocular lens, into the human eye in place of the natural lens, which had become cloudy. Since then, implantation of an intraocular lens has been widely practiced as treatment for cataract.
Japanese Patent Application Laid-Open (kokai) No. 58-146346 discloses deformable intraocular lenses that can be inserted into the eye through a small incision formed therein, such as a deformable intraocular lens that uses a deformable, elastic material having predetermined memory characteristics to form at least its optical portion, and a deformable intraocular lens that uses a deformable, elastic material having predetermined memory characteristics to form at least its optical portion and includes supports, which are adapted to support the optical portion within the eye and are made of a material different from that of the optical portion.
As shown in Japanese Patent Application Laid-Open (kokai) No. 4-212350, etc., the assignee of the present invention has proposed an insertion device for implantation of a deformable intraocular lens in the eye through a small incision formed in the eye. In the proposed device, the optical portion of a deformable intraocular lens is deformed to a smaller size before insertion thereof, through an operation of compressing, rolling, bending, stretching, or folding. The invention of such an insertion device has enhanced accuracy of and simplified a surgery for implantation of an intraocular lens in the eye.
FIGS. 10 and 11 show examples of deformable intraocular lenses. A deformable intraocular lens 1 shown in FIG. 10 includes a circular, optical portion 2 and a pair of supports 3. The optical portion 2 is made of a deformable, elastic material having predetermined memory characteristics. The supports 3 are made of a flexible material different from that of the optical portion 2. A base end portion 3a of each of the supports 3 is embedded in a circumferential portion of the optical portion 2. A linear projection portion 3b of each of the supports 3 is curved. The paired supports 3 are arranged symmetrically. FIG. 11A, and FIG. 11B, which is a sectional view taken along line XIB-XIB of FIG. 11A, show another deformable intraocular lens 1 made of a material having predetermined memory characteristics similar to that of FIG. 10. Two supports 4 project in opposite directions from a circumferential portion of a circular, optical portion 2.
FIG. 12 is an exterior view of an insertion device for folding either of the above-mentioned deformable intraocular lenses in half and inserting the folded lens into the eye through an insertion tube.
FIG. 12 is a partially cutaway perspective view of a conventional insertion device for a deformable intraocular lens. FIG. 14 is an enlarged perspective view of an insertion end portion of the insertion device. FIG. 15 is a cross sectional view taken along line XV-XV of FIG. 14. FIG. 16 is an enlarged perspective view of the insertion end portion of the insertion device which is used for description of operation.
In FIG. 12, reference numeral 11 denotes a device body; 12 denotes a push rod; 13 denotes a male-thread shaft; and 14 denotes a push-out mechanism.
Reference numeral 18 denotes an enclosing member. As shown in FIG. 13, the enclosing member 18 is provided with a lens receiving section 16 having a hinge portion 15. An insertion tube 17 projects from the front end of the lens receiving section 16. A tapered insertion end portion 17a of the insertion tube 17 has an axially extending slit 17b. The lens receiving section 16 has a stationary half sleeve 19 and a movable half sleeve 20, whose lower edge portions are connected together by means of the hinge portion 15. Stationary and movable press plates 21 and 22 project from the stationary and movable half sleeves 19 and 20, respectively.
The conventional insertion device having the above-described structure is used as follows. The intraocular lens 1 is placed on the lens receiving section 16 of the enclosing member 18 and is folded into a smaller size before being loaded onto the insertion device body 11.
Upon completion of loading of the intraocular lens 1, the male-thread shaft 13 of the intraocular-lens insertion device is rotated in order to screw-feed the push rod 12. As a result, a process of inserting the intraocular lens 1 into the eye starts.
The intraocular lens 1 is gradually pushed forward by the tip end of the push rod 12. When the intraocular lens 1 reaches the tapered insertion end portion 17a of the insertion tube 17, the axially extending slit 17b of the insertion end portion 17a opens gradually. As a result, stresses in the optical portion 2 of the intraocular lens 1, which has been folded at the base end portion 17c of the insertion tube 17, are gradually released at the insertion end portion 17a. Subsequently, the intraocular lens 1 is inserted into the eye from an open end 17d of the insertion tube 17.
The slit 17b holds the optical portion 2 of the intraocular lens 1 while sandwiching it, to thereby prevent abrupt ejection of the intraocular lens 1 into the eye. In addition, although the slit 17b releases stresses from the intraocular lens 1, the intraocular lens 1 is retained at the insertion end portion 17a, because cut surfaces located above and below the slit 17b hold the intraocular lens 1 from both sides thereof. Moreover, the slit 17b can control insertion speed of the intraocular lens 1 to match advancement speed of the push rod 12.
However, in the conventional insertion device, the insertion tube is not configured to prevent rotational movement about the insertion tube axis of an intraocular lens that is contained therein in a folded condition. As a result, as shown in FIG. 16, in some cases, the intraocular lens 1 within the insertion tube 17 may move unexpectedly in a rotational direction along the inner wall surface of the insertion tube 17 as represented by the dot-and-dash line.
Such an unexpected rotational movement of the folded intraocular lens within the insertion tube changes a positional relation between the folded intraocular lens and the slit formed in the insertion end portion of the insertion tube. As a result, the intraocular lens fails to project from the insertion end portion of the insertion tube in a desired condition. Accordingly, difficulty arises in controlling insertion of the intraocular lens with consistent repeatability in terms of insertion orientation and insertion speed. Therefore, a surgical procedure for implantation of the intraocular lens has required a great deal of skill.
Meanwhile, in order to prevent such an unexpected rotational movement of the intraocular lens, the assignee of the present invention has proposed an insertion device which includes an insertion tube having a guide portion that extends parallel to the axis of the insertion tube.